1. Who am I ?

a. I am ATP producing factory.

Ans: Mitochondria 

b. I am single layered, but maintain cellular osmotic pressure.

Ans: Vacuole 

c. I support the cell, but I am not cell wall. I have a body resembling net. 

Ans: Endoplasmic reticulum 

d. I am chemical factory of the cell.

Ans: Cytoplasm

e. Leaves are green because of me.

Ans: Chloroplast 

2. What would have happened ? If…….

a. RBCs had mitochondria.

Ans:

(i) The mitochondria would occupy space in the RBCs, thus allowing a lesser quantity of haemoglobin to be transported.

(ii) This in turn would cause less transport of oxygen by RBCs throughout the body.

(iii) Also, mitochondria, being the powerhouse of the cell, would consume oxygen for cellular respiration. It would thus cause a further decrease in the oxygen-carrying potential of these cells.

b. There had been no difference between mitochondria and plastids.

Ans: 

(i) Cellular respiration and ATP production would have occurred in plastids as well.

(ii) Animal cells also would have obtained coloration due to the presence of pigments in mitochondria.

(iii) The mitochondria would have stored food and other molecules, which would have been utilised directly for breakdown and cellular respiration to produce ATP.

c. Genes had been absent on the chromosomes.

Ans: 

(i) Hereditary information present on the genes would not be passed from parents to offspring.

(ii) Since genes contain information for protein synthesis, in their absence, no proteins would be synthesized and important cellular processes would not occur.

(iii) Genes in the nucleus control all cellular activities and growth. Hence, in its absence, no growth or development would be possible.

(iv) The genes regulate and coordinate all cell activities, and hence multicellular organisation would also be difficult in the absence of genes on chromosomes.

d. Plasma membrane had not been selectively permeable.

Ans:

(i) If the plasma/cell membrane was completely permeable, it would allow entry of all molecules into the cell.

(ii) This would include toxins, etc., that could damage the cell.

(iii) If the plasma membrane were impermeable, it would be difficult for the cell to survive.

(iv) The cell does not produce all molecules and takes up certain important molecules from the surrounding environment.

(v) It would also not allow the disposal of waste materials and result in cell toxicity.

(vi) Osmosis may not occur, and cells may be harmed.

e. Plants lacked anthocyanin.

Ans: 

(i) Plant parts would lack red, blue, or purple coloration.

(ii) The loss of these pigments in flowers may cause a loss of colour, resulting in no pollination since the appropriate pollinators, like insects, birds, etc., would not be attracted to the flowers.

(iii) The absorption of light by plants containing these pigments would be disturbed.

(iv) Anthocyanins may have a protective role in plants. Thus, plants would lack this protection in the absence of anthocyanin.

3. Who is the odd man among us? Give reason.

a. Nucleolus, mitochondria, plastids, endoplasmic reticulum

Ans: Plastids

Plastids are present in plant cells only, whereas the rest are present in both plant and animal cells.

b. DNA, Ribosomes, Chlorophyll

Ans: Chlorophyll

Chlorophyll is present only in plant cells, whereas DNA and ribosomes are present in both plant and animal cells.

4. Give functions.

a. Plasma membrane 

Ans: The functions of the plasma membrane are as follows:

(i) The structure of the plasma membrane allows the passage of some substances into the cell while preventing the entry of others; hence, it is called a selectively permeable membrane.

(ii) This property of the cell membrane allows the entry of useful molecules like water, salt, and oxygen and also the removal or exit of carbon dioxide and other waste materials from the cell.

(iii) Homeostasis is established by the plasma membrane, due to which changes in the external environment of the cell do not change the cellular environment.

b. Cytoplasm

Ans: The functions of the cytoplasm are as follows:

(i) The cell cytoplasm provides a medium for the suspension of various cell organelles within the cell.

(ii) Chemical reactions that take place within the cell occur mostly in the cytoplasm.

(iii) The cytosol (region of cytoplasm apart from cell organelles) is composed of vital substances like amino acids, glucose, vitamins, etc., essential to the cell.

c. Lysosome

Ans: Lysosomes have the following functions:

(i) Lysosomes play an important role in the immune system of the body by destroying viruses and bacteria that attack the cell.

(ii) They act as demolition squads that destroy worn-out cell organelles and organic debris by cellular digestion (autophagy).

(iii) They are also known as “suicide bags of the cell,” as they burst and enzymatically digest old or damaged cells by autolysis.

(iv) They also digest stored food content such as proteins and fats to provide energy to the cell if it is starving.

d. Vacuole

Ans:

The following are the functions of vacuoles:

(i) Maintaining the osmotic pressure of the cell.

(ii) Storing the important by-products or end products of metabolic reactions, e.g., proteins, water, etc.

(iii) They may store waste products in animal cells. Also, in Amoeba, food is stored in food vacuoles before digestion.

(iv) In plant cells, the vacuoles are filled with cell sap and provide turgidity and rigidity to the cells.

e. Nucleus

Ans:

The functions of the nucleus are as follows:

(i) It controls cell division and all the metabolic activities of the cell.

(ii) Genes on the chromosomes present in the nucleus are responsible for the transfer of hereditary characteristics from parents to offspring.

5. Who gives me the colour? (Select the correct option.)